Smurfkicker

Hi guys. I was hoping someone could help me with something really basic. I'm stumped by number 4 in the install instructions. "Open a terminal and cd into the disk image, you'll need to run commands from here". Not sure what the terminal is or what I should be using to open it. I've opened the dmg, then the zip inside that and I have a file called app, but there doesn't seem to be anything executable in there. Can someone point me in the right direction?